CN113795197A

CN113795197A - Method for improving radiological images during angiography

Info

Publication number: CN113795197A
Application number: CN202080033590.1A
Authority: CN
Inventors: S·赞诺利; E·阿尔蒂尼
Original assignee: Angiodroid Srl
Current assignee: Angiodroid Srl
Priority date: 2019-05-07
Filing date: 2020-05-07
Publication date: 2021-12-14
Also published as: IT201900006616A1; EP3966781A1; US20220230368A1; WO2020225764A1

Abstract

The invention describes a method for obtaining improved digital radiological images during a Digital Subtraction Angiography (DSA) intervention by introducing a contrast agent consisting of CO2 or other fluid in an examination region (Z) of a human or animal body and creating a digital radiological image (IMC1, IMC2, IMC3.. IMCn) of the examination region (Z) upon input of the contrast agent. The mask image (IMM1, IMM2, IMM3.. IMMn) of the same region (Z) is subtracted with each image (IMC1, IMC2, IMC3.. IMCn) with contrast agent, resulting in a series of "clean" digital radiological images with limited noise. According to the method, each mask image (IMM1, IMM2, IMM3.. IMMn) is composed of an image with contrast (IMC (2-1), IMC (3-1.. IMC (n-1)) which immediately precedes the currently obtained image with contrast, or is obtained by a weighted combination thereof.

Description

Method for improving radiological images during angiography

Technical Field

The present invention relates to a device for diagnostic investigation of a human or animal body, in particular by angiography, and to a method for improving the representation and visual effect of images obtained by means of the device.

Background

As is known, angiography is a radiodiagnostic practice carried out by injecting a contrast agent into a blood vessel and simultaneously acquiring a series of radiological images, while the contrast agent flows inside a vase (vase), increasing the contrast between it and the surrounding tissue.

Radiographic techniques are used to produce angiograms, i.e. representative images of the affected area, which allow detailed analysis of the vessel to examine any wall lesions, stenosis, occlusions, aneurysms, fistulas, etc.

Generally, these procedures are performed in a vascular radiology department, equipped with the necessary equipment to perform radiological techniques, whose radiological systems allow the storage and analysis of images using digital techniques.

Digital medical images are best characterized in that they can be processed and refined on a computer, even later, by using appropriate digital algorithms, so that more accurate and detailed information about the condition of the vessel under study can be obtained.

The image to be analyzed is obtained by means of an X-ray beam which is directed in such a way as to pass precisely through a region of interest of the patient's body.

For this reason, X-rays are often used in conjunction with fluid contrast agents, injected through a catheter in the interventional region, to produce more detailed images of organs and vessels. In the radiographs obtained, most contrast fluids are "radiopaque," have significant X-ray absorption, and cause the blood vessels to appear differently blackened relative to the tissue.

In addition to having a high radiation absorption coefficient, in order to clearly describe the structure of the vessel into which it is injected, the contrast agent must have a low viscosity, high water solubility and good biological tolerance. Its elimination usually occurs in the kidneys and urinary tract.

Disclosure of Invention

Technical problem

The most commonly used contrast agents in angiography are based on iodine, which is highly radiopaque under X-rays, but in some cases it causes allergies and exhibits non-negligible nephrotoxicity. Therefore, efforts have been made to use alternative means, such as the use of high purity carbon dioxide, injected according to controlled volume and pressure conditions, which have shown significant advantages compared to conventional and still widely used contrast agents.

This gas is particularly effective in peripheral angiography, since once injected into a blood vessel it allows to obtain a good radiographic view of the injection area, without problems of tolerance and handling, which can be quickly and completely eliminated through the lungs.

Like iodinated contrast agents, CO2 is introduced into the blood vessel through a catheter, but it does not dilute in the blood, but instead creates a bubble that is dragged along by the blood flow.

The different absorption of X-ray radiation by the tissue and the bubbles (to a much lesser extent) highlights the blood vessels through which the bubbles pass, so that their structure can be reconstructed.

During the movement of CO2 bubbles within the progressively smaller blood vessels, gas diffuses through the vessel wall, dissolves in the surrounding tissue, and the bubbles disappear.

For this reason, the introduction pattern (pressure and volume) of the gaseous contrast agent is limited by the conditions required to obtain a sufficiently complete vascular filling of the interventional region and determines the quality and sequence of the radiological images.

Since the distinction between the vascular structure of interest and the other elements surrounding it occurs on the basis of the different absorption of radiation by the introduced contrast agent, which in any case determines a difference in light intensity that is not very significant compared to the variations caused by the surrounding tissue, with the advent of digital radiology, a technique known as subtraction angiography or DSA (digital subtraction angiography) has been established, according to which the image acquired and digitized in the presence of the contrast agent (CO2) is subtracted, pixel by pixel, from the image acquired before the introduction of the contrast agent (mask).

This procedure allows to effectively remove from the image contaminations of static and repetitive structures that occur at constant intensity before and after the introduction of the contrast agent.

The process of image subtraction is used to eliminate background information from the diagnostic image that is considered useless and is effectively used to study blood vessels, which are usually hidden in the image by bone and surrounding tissue.

The simplest subtraction consists of acquiring a single image before introducing the contrast agent (mask) and then subtracting this single image from subsequent images obtained at a predetermined suitable frequency after a dose of contrast agent has been input.

This technique allows to obtain a particularly detailed image of the only blood vessel in which CO2 has been introduced, in which the bubble has formed and is moving.

However, between the moment of acquiring the first image and subtracting it from below, dynamic events often occur in which the patient or organ may have moved slightly, for example the gas region present in the abdomen has moved, the air in the bronchi or lungs increases/decreases due to the influence of breathing, etc.

These events determine the difference between the detected successive images and the initial "mask" image, which is not due to injected contrast agent, but is a false diagnostic indication provided by the imaging system associated with the radiological apparatus.

The image subtraction technique is not always sufficiently effective in view of all dynamic variations and errors introduced by patient motion during the time interval in which the digital subtraction angiography procedure associated with the use of CO2 as a contrast agent occurs.

Furthermore, in order to widen the area highlighted by the moving bubble, several temporally successive images may be superimposed, in which case the same interference and "noise" itself is not repeated in the various images, remaining in the final image at different points, and even the mask is removed, it is ineffective, so that the diagnostic information is not useful even if it is not well suited to distinguish the structure of the examined organ.

Object of the Invention

The main object of the present invention is to propose a method applied to an imaging procedure for preparing images displayed on a monitor handled by the surgeon, allowing to carry out a DSA (digital subtraction angiography) procedure by automatically subtracting the most suitable image from the image acquired during the introduction of the contrast agent consisting of CO 2.

It is another object of the present invention to enable a physician to obtain images quickly and expeditiously, without the need for intervention by other personnel, to allow the necessary assessment to guide the continuation of a current exam while still obtaining the best images after the exam.

It is another object of the invention to provide an algorithm that is able to automatically perform a subtraction between the most suitable images according to DSA techniques, and the result of which allows the above mentioned objects to be achieved.

It is also an object of the invention to propose a method which can be easily used with currently operating DSA angiography devices and which implements, integrates and/or replaces elements which do not involve substantial structural and functional reconfiguration of the device.

The above objects are fully achieved by the claimed method for performing angiography using DSA technique and by the use of contrast agents consisting of carbon dioxide, according to the preferred but not exclusive embodiments of the invention.

Drawings

Features of the present invention which will become apparent from the claims are emphasized in the following detailed description with reference to the drawings, in which:

figure 1 shows a schematic view of a device for performing an angiographic examination or intervention using carbon dioxide as contrast agent and implementing the method according to the invention;

2A, 2B, 2C, 2D, 2E and 2F, showing an exemplary sequence of digital radiological images obtained without application of DSA image subtraction;

3A, 3B, 3C, 3D, 3E and 3F, showing an example sequence of digital radiological images obtained after application of a digital subtraction angiographic image, according to the method object of the invention.

Detailed Description

With reference to fig. 1, and with reference to a preferred but not exclusive embodiment of the invention, a device for performing an angiographic intervention, for example for examining the condition of a patient's vascular system features, is generally indicated at 100.

The apparatus 100 comprises means 6 for performing dosage and adjustment of a contrast agent used in angiography, the means 6 operating according to known methods and therefore will not be described in greater detail.

The device 6 uses a gas-phase contrast agent, preferably constituted by CO2 (carbon dioxide), which is injected into the vascular system of the patient P through a catheter 7 of a known type.

The catheter 7 is introduced into a blood vessel (e.g. the femoral artery), for example at the groin, until it reaches the examination zone Z; this step also follows known and commonly practiced methods.

Although the method proposed herein is primarily intended for angiography using gaseous contrast agents, it must be understood that the same inventive principles, and in particular the method in question, may equally advantageously be used for administering contrast agents in the liquid phase, without however requiring substantial changes to the phase on which the method itself is based.

As shown in fig. 1, the patient P is usually lying in a supine position on a table 10 corresponding to the radiation apparatus 100, the radiation apparatus 100 comprising an X-ray generator 8 and a collecting device 9, the X-ray generator 8 being located above the table 10 and the collecting device 9 being sensitive to radiation emitted by the generator 10 and being located below the table 10.

The generator 8 and the acquisition device 9 and the means 6 for repeatedly delivering a dose of a contractile medium are connected to a control unit 11, the control unit 11 managing and coordinating the operation of these devices to generate a series of images taking into account the displacement of the air bubbles in the blood vessels and the diffusion time of the gas in the blood.

Also contained in the control unit 11 is an imaging system connected to means for processing the signals received by the acquisition device 9, having the function of creating and processing corresponding digital images, which are then displayed on a display 12 accessible to the surgeon.

The introduction of the preselected and adjustable CO2 dose is performed at a frequency determined by the examining surgeon, which is substantially dependent on the time it takes for the bubbles to move the blood and through the examination region.

Illustratively, in the peripheral vascular system, the frequency of image recovery remains between 2 and 7 times per second, while when the angiographic intervention affects a region characterized by more pronounced dynamics, such as the heart, or more likely the coronary arteries, the acquisition frequency of the digital images may rise to 25 times per second.

For implementing the method in question, and for subsequent processing and/or display, the digital image obtained is recorded in a memory (not shown) connected to the control unit 11 or internal to the control unit 11, which memory can then be called up according to known methods.

For better illustration and understanding of the invention, the image "contrast image" IMC is defined hereinafter as the original image obtained after introduction of the contrast medium and not subjected to any subtraction process.

By "IMM mask image" we mean the image used to subtract from the IMC contrast image.

Finally, by "clean image" IMP we mean the image processed by subtracting the IMM mask image from the IMC contrast image.

According to the invention, the method provides for producing a series of clean digital radiological images IMP1, IMP2, IMP3.. IMP.. which are free of noise and "noise", produced by subtracting the IMC (2-1), IMC (3-1.. IMC (n-1) contrasts from the corresponding mask images IMM1, IMM2, IMM3.. IMP.. from the previously acquired images, when the contrast agent diffuses in the examination zone Z.

As is evident from the above, the digital radiological images are obtained by means of an imaging procedure starting from a representation of the examination zone Z produced by X-rays passing through the examination zone and detected by suitable sensitive detection means 9 constituted by acquisition devices.

According to a preferred embodiment of the method object of the invention, each mask image IMM1, IMM2, IMM3.. IMMn is used to obtain a clean image IMP1, IMP2, IMP3.. IMPn from each image IMC1, IMC2, IMC3.. IMCn with contrast, which is achieved using an image IMC (2-1), IMC (3-1).. IMC (n-1) with contrast agent immediately preceding the current image.

Indeed, after the first mask image IMM1 obtained in the absence of contrast agent and subtracted from the first contrast image IMC1, the latter is used as the mask image IMM2 for subtraction in the subsequent contrast image IMC 2.

The cycle is then repeated until the end of the angiographic examination.

Thus, it is staged, in anticipation of:

a) obtaining a mask image IMM1 prior to introducing the contrast agent; a representation of this image can be seen in fig. 2A, where some air bubbles H, K present in the intestine can also be observed, covering the examination area and disturbing the vision; in FIG. 3A, after subtracting the mask image, the same image of FIG. 2A can be seen;

b) obtaining an image IMC1 with a contrast agent introduced into the blood vessel; in fig. 2B, contrast agent has been introduced, but organs H and K prevent proper viewing of the vessel;

c) Subtract mask image IMM1 from image IMC1 with contrast agent to obtain a first clean image IMP 1; the image of FIG. 3B is the result of subtracting the image of FIG. 2A from the image of FIG. 2B; the disappearance of organs H and K and the presence of contrast agent C along the vessel in question can be seen;

d) obtaining a new image IMC2 with contrast, as shown in FIG. 2C;

e) prior to using the currently acquired radiological image of contrast IMC2, a new mask image IMM2 consisting of the contrast image IMC (2-1), actually the image of FIG. 2B, is acquired;

f) subtracting the corresponding mask image IMM2, consisting of the previous contrast image IMC (2-1), from the contrast image IMC2 to obtain a corresponding clean radiological image IMP 2; the obtained image is the image of fig. 3C obtained by subtracting the image of fig. 2B from the image of fig. 2C; note the swelling of contrast agent C along the vessel;

g) repeating the steps b, c and D until the examination is finished, and obtaining the images indicated by the figures 2D, 2E and 2F and the respective clean images indicated by the figures 3D, 3E and 3F; in a 3F image you can see that the contrast agent is flowing in the outermost part of the vessel (relative to the image) and is leaving the examination area.

In order to subtract the mask images IMM1, IMM2, IMM3.. IMMn from the contrast images IMC1, IMC2, IMC3.. IMCn, suitable algorithms are provided which operate in the control unit 11 for processing and displaying the images.

These algorithms are particularly capable of subtracting the logic states that make up the digital mask images IMM1, IMM2, IMM3.. IMMn from the corresponding logic states that make up the digital images IMC1, IMC2, IMC3.. IMMn with contrast.

In contrast to the preferred embodiment described above, an alternative embodiment of the method according to the invention provides for obtaining the aforementioned mask images IMM1, IMM2, IMM3.. IMCn by processing at least two images with a contrast medium before the current contrast image (IMC2, IMC3, IMCn). The processing may, for example, comprise calculating a weighted average of corresponding pixel values in two or more previous images.

This variant, in certain operating situations, allows to obtain more efficient mask images IMM1, IMM2, IMM3.

According to another embodiment of the method, a weighted clean image impp is obtained, wherein each pixel is selected from equivalent pixels of s previous clean images (IMPn-1, IMPn-2.. IMPn-s) obtained as described above, wherein the value of the parameter s is defined by the operator. In particular, to define a given pixel of the current weighted clean image IPMP, the pixel with the highest difference value is selected among s pixels of the previous clean image. In this way, according to the method, each clean weighted image impp contains, in each of its own pixels, the highest difference values among those previously calculated for the preceding s clean images.

In essence, the value of parameter s defines the analysis "depth" of the clean image obtained in the previous cycles to calculate each pixel of the new weighted clean image IMPPn.

For example, if the parameter s is defined to be 3, considering an image with a pixel matrix (r, c) of size 1024 × 1024, the order in which the clean image and the corresponding clean weighted image are obtained in the first 6 processing cycles will be as follows:

IMM1＝IMC1

IMP2＝IMC2-IMM1 IMM2＝IMC2:IMPP2＝IMP2

IMP3＝IMC3-IMM2 IMM3＝IMC3:IMPP3＝IMP3

IMP4＝IMC4-IMM3 IMM4＝IMC4:IMPP4(r，c)＝maxvalue(IMP4(r；c)，IMP3(r；c)，IMP2(r；c))*；

IMP5＝IMC5-IMM4 IMM5＝IMC5:IMPP5(r，c)＝maxvalue(IMP5(r；c)，IMP4(r；c)，IMP3(r；c))*；

IMP6＝IMC6-IMM5 IMM6＝IMC6:IMPP6(r，c)＝maxvalue(IMP6(r；c)，IMP5(r；c)，IMP4(r；c))*；

repeating for each pair of pixels forming the image, i.e. r 1/1024/c 1/1024

In this way, the software implementing the method embodiment described above allows you to "drag" a "frame" window of length determined in real time by the operator, behind the pixel with the higher value (i.e. the pixel containing more useful information).

The clean images IMP1, IMP2, IMP3.. IMPn, or IMP1, IMP2, IMPP3.. impnp, obtained with the present method can be superimposed on one another to obtain angiograms a1, a2 with a more complete representation of the examination zone Z, including multiple injections of contrast agent.

Alternatively, the clean images IMP1, IMP2, IMP3.. IMPn, or IMP1, IMP2, IMP3.. IMPP, or angiograms a1, a2 obtained therefrom, may be put together and connected to obtain a wider Z examination region.

Inside the control unit 11, computer program means are provided, consisting of a series of readable and executable instructions of a microprocessor, for realizing the method object of the invention.

The programmer incorporates the above-described algorithm for superimposing two or more clean images IMP1, IMP2, IMP3.. IMPn, and/or for combining and connecting two or more angiograms a1, a2 to obtain a larger range of examination zone Z.

At the end of the procedure, the surgeon may review all the images taken during the angiographic intervention and find those images in time that are most suitable for the mask images that make up each image IMC1, IMC2, IMC3.. IMCn with contrast, perform the subtraction and obtain the best image to deepen the study of the case or for disclosure or other purposes.

It will be apparent to those skilled in the art that the method presented herein allows to achieve all the above objects.

As it applies to imaging procedures that prepare images for display on a monitor for use by the operating surgeon, a digital subtraction angiography system may be implemented by subtracting the most appropriate image from the image obtained gradually as the contrast agent is introduced. No other technician intervention is required at the CO2, allowing the surgeon to continue the angiographic examination with the appropriate images obtained in real time.

However, it is still possible to obtain an optimal image after inspection.

It is also possible to superimpose different radiological images, obtaining a more complete and extended image of the region of interest with respect to the image obtained with each entrance of contrast agent.

The possibility of wishing to be completely self-contained by the surgeon and to make the examination easier constitutes an effective incentive to diffuse the digital subtraction angiography technique using CO2 as contrast agent, limiting (if not eliminating) the interferences, side-effects and possible complications caused by the use of contrast agents themselves, in particular iodinated contrast agents.

Finally, the proposed method can be easily implemented in currently operating digital subtraction angiography devices, adding and/or replacing most of the computer elements, which does not involve substantial structural reconfiguration of such devices.

It is to be understood that the above has been described by way of non-limiting example only. Thus, possible modifications and variations of the invention are considered to fall within the scope of protection consistent with the present technical solution, as described above and claimed.

Claims

1. Method for improving radiological images during angiography, the improved radiological images being realized by introducing a fluid contrast agent in an examination region (Z) of a human or animal body, and by realizing digital radiological images (IMC1, IMC2, IMC3.. IMCn) of the same examination region (Z) when using the contrast agent, and wherein mask images (IMM1, IMM2, IMM3.. IMMn) of the same region (Z) are planned to be subtracted from each image (IMC1, IMC2, IMC3.. IMCn) with the contrast agent, resulting in a series of noise-free clean digital radiological images (IMM1, IMM2, IMM3.. IMMn),

The method is characterized in that each mask image (IMM1, IMM2, IMM3.. IMMn) comprises at least one image with contrast (IMC (2-1), IMC (3-1.. IMC (n-1)), which is selected from at least one image preceding the currently obtained image with contrast (IMC (2-1), IMC (3-1.. IMC (n-1)).

2. The method of claim 1, wherein the method provides:

a) obtaining a mask image (IMM1) prior to inputting the contrast agent;

b) obtaining an image (IMC1) with a contrast agent;

c) subtracting the mask image (IMM1) from the image with contrast agent (IMC1) to obtain a first clean image (IMP 1);

d) obtaining a new image with contrast agent (IMC 2);

e) obtaining a new mask image (IMM2, IMM3.. IMMn) consisting of an image with contrast agent (IMC (2-1), IMC (3-1.. IMC (n-1)), the image with contrast agent (IMC (2-1), IMC (3-1.. IMC (n-1)) immediately preceding the currently obtained image with contrast agent (IMC2, IMC3.. IMCn);

f) subtracting respective mask images (IMM2, IMM3.. IMMn) composed of previous radiological images (IMC (2-1), IMC (3-1.. IMC (n-1)) with contrast agent from the images (IMC2, IMC3.. IMCn) with contrast agent, obtaining respective clean radiological images (IMP2, IMP3.. IMPn);

g) And repeating the steps b, c and d until the examination is finished.

3. The method of claim 1, wherein the method provides:

a) obtaining a mask image (IMM1) prior to inputting the contrast agent;

b) obtaining an image (IMC1) with a contrast agent;

d) obtaining a new image with contrast agent (IMC 2);

e) obtaining a new mask image (IMM2, IMM3.. IMMn) comprising a weighted average of at least two images with contrast agent preceding a currently obtained image with contrast agent (IMC2, IMC3.. IMCn);

f) subtracting the new mask image (IMM2, IMM3.. IMMn) from the image with contrast agent (IMC2, IMC3.. IMCn) to obtain a corresponding "clean" radiological image (IMP2, IMP3.. IMPn);

g) and repeating the steps b, c and d until the examination is finished.

4. A method according to any one of claims 1 to 3, characterized in that it further comprises the definition of a depth parameter "s", and the implementation of a clean weighted image (impnp) based on said parameter, wherein each pixel is selected from s equivalent pixels of the clean image (IMPn-1, IMPn-2.. IMPn-s); the definition of each pixel of each of the aforementioned clean weighted images (IPMPn) comprises selecting the one with the highest difference among the s pixels of the previous clean image.

5. A method as claimed in any one of claims 1 to 3, characterized in that said digital radiological images (IMC1, IMC2, IMC3.. IMCn) are obtained by an imaging process starting from a representation of the examination zone (Z) produced by X-rays passing through it and detected by suitable sensitive detection means (9).

6. The method according to any of the preceding claims, wherein the contrast agent consists of CO 2.

7. Method according to any of the preceding claims, characterized in that the subtraction is performed by means of a suitable algorithm adapted to subtract the logical states constituting the digital mask image (IMM1, IMM2, IMM3.. IMMn) from the respective logical states constituting the digital image with contrast (IMC1, IMC2, IMC3.. IMMn).

8. Method according to one or more of the preceding claims, characterized in that two or more clean images (IMP1, IMP2, IMP3.. IMPn) are superimposed on each other to obtain angiograms (a1, a2) with a more complete representation of the examination zone (Z), including multiple injections of contrast agent.

9. The method according to one or more of the preceding claims, characterized in that two or more angiograms (A1, A2) are combined and combined to obtain an image of the examination zone (Z) plus the extension.

10. Computer program means designed to implement a method according to one or more of claims 1 to 8 and adapted to perform:

a) obtaining a mask image (IMM1) prior to inputting the contrast agent;

b) obtaining an image (IMC1) with a contrast agent;

d) obtaining a new image with contrast agent (IMC 2);

e) obtaining a new mask image (IMM2, IMM3.. IMMn) consisting of the image with contrast agent (IMC (2-1), IMC (3-1).. IMC (n-1)) before the currently obtained image with contrast agent (IMC2, IMC3.. IMCn);

g) and repeating the steps b, c and d until the examination is finished.

11. The program device of claim 9, for overlaying two or more clean images (IMP1, IMP2, IMP3.. IMPn) to obtain angiograms (a1, a2) with a more complete representation of the examination zone (Z), including multiple injections of contrast agent.

12. Procedure arrangement according to claim 9 or 10, for accessing and connecting two or more angiograms (a1, a2) to obtain an image of a larger examination zone (Z).